The invention relates to passive ossicular prosthesis designed to replace or bridge at least one component of the human ossicular chain. The ossicular prosthesis comprises an elongated, sound-conducting prosthesis body, which at one end has a first coupling element designed in the form of a bight. The bight is made of a strip-shaped metallic material, is partially open toward the outside via a gap-type opening and encloses the component of the ossicular chain or the actuator end piece for mechanical connection to the long process of incus (=“incus”), the manubrium of malleus (“malleus”), or an elongated actuator end piece of an active hearing aid. Post-operatively, the bight encloses the long process of incus, the manubrium of malleus, or the actuator end piece in a non-positive manner and, intraoperatively, can be deformed, using crimping tongs, in the middle ear for the fixation and permanent attachment of the first coupling element to the long process of incus, the manubrium of malleus, or the actuator end piece. The prosthesis body comprises, at the other end thereof, a second coupling element for mechanical connection to a further component or parts of a component of the ossicular chain or directly to the inner ear.
A known passive ossicular prosthesis is described and shown in DE 20 2014 100 093 U1. Therein, the special problems associated with the intraoperative crimping of bight-shaped parts of a first coupling element are described, in particular, although merely in conjunction with the bridging of parts or components of the ossicular chain, but not for coupling the passive prosthesis to an actuator end piece of an active hearing aid.
Similar known passive ossicular prostheses, which are typically designed as stapes prostheses, are described in U.S. Pat. No. 3,711,869 and U.S. Pat. No. 3,931,648. Therein, the first coupling element is not designed as a bight, but rather as a clip that is intended to be self-closing and self-retaining via the spring properties thereof, and is therefore not crimped, as is the case with the bight of a prosthesis of the type in question.
In the case of the ossicular prostheses known from EP 2 385 808 B1 or EP 2 583 639 A1, however, a first coupling element is made of a strip-shaped, flexible material and is provided with slits parallel to the longitudinal axis of the component of the ossicular chain to be enclosed. However, the geometric design of the coupling element used therein is not bight-shaped, but rather is designed as a loop that is intraoperatively inserted, via the free end thereof, into an eyelet intended therefor on the prosthesis body. An attachment step, which is comparable to the crimping procedure used to intraoperatively affix the bight according to the initially cited document DE 20 2014 100 093 U1, is not carried out with these known prostheses.
Ossicular prostheses in which the first coupling element is actually designed as a bight are shown and described in U.S. Pat. No. 6,554,861 and DE 10 2007 008 851 B3, for example. Therein, however, in contrast to the initially mentioned prostheses of the type in question, the bight is not made of strip-shaped metallic material, but rather of round wire material. The crimping procedure for same is therefore considerably different than for the prostheses of the type in question in terms of the intraoperative attachment of the bight.
The human middle ear comprising the ossicles thereof has the function of transmitting the sound waves impacting the tympanic membrane via the external auditory meatus to the inner ear, which is filled with fluid. The three ossicles are the hammer (lat. malleus), which is attached to the tympanic membrane, the stirrup (lat. stapes), which is connected via the footplate (lat. basis stapedis) thereof to the inner ear and the anvil (lat. incus), which is located between the hammer and the stapes and is hingedly connected thereto. For example, otosclerosis is a disease of the human petrosal bone (=bone in which the entire ear is seated), in which inflammation-like bone remodeling processes can result in fixation of the stapes, which normally swings freely.
As a result, the sound signal is transmitted incompletely or not at all via the ossicular chain to the inner ear, thereby resulting in hearing loss.
Ossicular prostheses are used, in general, to improve sound transmission in patients having different pathologies. Ossicular prostheses are used to improve or merely enable the transfer of sound from the tympanic membrane to the inner ear in cases in which the ossicles of the human middle ear are missing or damaged, either entirely or partially. The passive ossicular prosthesis has two ends. Depending on the specific circumstances, one end of the ossicular prosthesis is attached to the tympanic membrane, an ossicles, or the actuator end piece of an active electronic hearing aid and the other end of the ossicular prosthesis is attached, e.g., to the stapes of the human ossicular chain, or is inserted directly into the inner ear.
Three types of ossicular prostheses that are used particularly frequently are stapes prostheses, partial prostheses and total prostheses. Stapes prostheses are usually fixed on the long process of incus and extend via a piston into the inner ear or are seated, with the piston, on a piece of tissue that seals the inner ear. Partial prostheses typically bear via a top plate against the tympanic membrane and establish a connection to the head of the stapes. Total prostheses connect the tympanic membrane to the base of stapes.
In addition, a distinction is generally made between passive ossicular prostheses and active hearing implants having electronic amplification elements, which are operated via an external energy part. The initially defined ossicular prosthesis of the type in question is a passive prosthesis in which a coupling element is provided at the upper end of the prosthesis body and is crimped with the long process of incus (=“incus”), the manubrium of malleus (“malleus”), or an actuator end piece of an active hearing aid.
The methods and problems associated with the attachment of such ossicular prostheses having a bight-shaped coupling element are extensively described in the scientific literature.
Stapes prostheses designed specifically for connection to the incus, which comprise, as the first coupling element, a bight, a loop, or a clip for crimping around the incus are extensively described in respect of their geometric design, the details of their coupling to the incus, and in respect of their mode of operation in the following, for example, in Fritsch, et al., “History of Otology: Phylogeny of the Stapes Prosthesis”, Otology & Neurotology, 29: 407-415, 2008; in Fontana, et al., “A scanning electron microscopic study of crimping of stapedial prostheses”, Auris Nasus Larynx 39 (2012) 461-468; in Kwok, et al., “Stapes Surgery: How Precisely Do Different Prostheses Attach to the Long Process of Incus with Different Instruments and Different Surgeons?”, Otology & Neurotology, 23: 289-295, 2002; and in a textbook “Middle Ear Surgery” by Hildmann and Sudhoff, published by Springer-Verlag Berlin Heidelberg, ISBN: 978-3-540-22201-9, 2006 (see in particular, page 117). In addition, in the article by Huber, et al., “Stapes Prosthesis Attachment: The Effect of Crimping on Sound Transfer in Otosclerosis Surgery”, Laryngoscope 113: May 2003, there is a detailed discussion of the problems that can result from the current crimping techniques used with such stapes prostheses.
The known crimp stapes prostheses, which usually comprise a piston for coupling to the inner ear at the lower end of the prostheses, are typically applied on the long process of incus, for example, by crimping or alligator pincers. This application comprises simply placing or laying the bight on the incus. In the next step, the bight is closed with the pincers. This closing process is still considered to be the most difficult part of the middle ear operation, namely, because the closing process itself can cause the piston to be moved medially into the inner ear. These movements can result in relatively minor but also serious inner ear damage, which can have a negative effect on the patient's post-operative state of health.
Since the incus is basically never round or oval, due to anatomical variation, but rather typically has a highly complex cross-section, it is advantageous when the bight has the least possible memory spring effect. Therefore, when the bight is closed with the pincers, the surgeon would like to achieve the most gentle, soft, and permanent plastic deformation possible without any subsequent recoil.
The disadvantage of the initially described ossicular prosthesis of the type in question, which is known from DE 20 2014 100 093 U1, for example, is the ever-present tendency for the metallic material of the bight to recoil during crimping due to the aforementioned mechanical memory spring effect, which becomes apparent as the strip material bending. The intrinsic stiffness of the material also causes problems, however, in respect of a deformation of the coupling element in the intraoperative processing that is as precise and permanent as possible.
The problem addressed by the present invention is that of improving a passive ossicular prosthesis of the initially described type in question using the simplest technical means possible and as cost-effectively as possible such that said ossicular prosthesis can be produced using particularly simple and economical process engineering, and in which the above-described mechanical memory spring effects occur not at all or are markedly reduced, wherein the intrinsic stiffness of the material should also be reduced by the greatest extent possible.